The midfielder missed the games against West Bromwich Albion, Queens Park Rangers and Fulham before making a goalscoring return in the 2-1 win over Luton last Saturday.
At the age of 35, Gallagher says he sometimes has to take the sensible option of sitting out training and going in the gym instead in order to manage such injuries.
North End could do with him firing on all cylinders as they face back-to-back away games at Cardiff and Leeds over the next week.
Gallagher said: “I’ve had an issue with my Achilles for the last month and a bit.
“I was managing it to get through games but then it got to the point where it was a bit too sore to carry on and I had to rest it.
“I’m sometimes the type not to say anything, who just wants to keep on playing.
“But then you get to the stage where I’m hampering myself and more importantly the team because I’m not able to play at full tilt.
“You can only do that for so long before it catches up on you.
“Sometimes you have to make the right decision, put your hand up and say it needs someone else to play.
“In this team there are boys who have come in and put in a great shift.”
Gallagher showed few signs of discomfort against Luton, scoring PNE’s opening goal from a rebound after his penalty had been saved.
Late in the contest he was involved in the scramble in the Luton box which led to Jayden Stockley netting North End’s winning goal.
Said Gallagher: “I had an injection in the Achilles to settle it down and I’ve done a lot of work in the gym to try and help the recovery.
“It’s settled down but it’s still there a bit. I’m going to manage it, decide when I can train and can’t train.
“In training I like to be the first out there and the last in – I still want to learn.
“Sometimes though, you have to think that it is not the best thing to train that day and to go in the gym instead.
“I’ve got that relationship with the manager and staff where if I want a day in the gym to recover, they understand.”
Gallagher was content with his display against Luton despite a couple of passes going astray.
“I tried to express myself and that is how I like to play,” said Gallagher.
“Passes sometimes don’t reach their target and I could just play five-yard passes.
“But if you want to stretch the game, play in behind, you have to take a risk and play it over a longer distance.
“Some passes come off, some don’t. That is football.”